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notsponge [240]
3 years ago
12

1) A car is traveling down the interstate at 37.1 m/s. The driver sees a cop and quickly slows down. If the driver slows to 29.8

m/s in 3 seconds, what is the acceleration of the car?
2) While cleaning you lift an 87.3 N box up to a shelf that is 2.04 m above the ground. How much work was done on the box?

3) A child runs up the stairs and does 1250 J of work. If the child generates 267 W of power how long did it take for the child to run up the stairs?
Physics
1 answer:
dlinn [17]3 years ago
3 0

Explanation:

1. Acceleration is the change in velocity over time.

a = Δv / Δt

a = (29.8 m/s − 37.1 m/s) / 3 s

a = -2.43 m/s²

2. Work equals force times distance.

W = Fd

W = (87.3 N) (2.04 m)

W = 178 J

3. Power is work per time.

P = W / t

267 W = 1250 J / t

t = 4.68 s

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Derive an expression for the energy needed to launch an object from the surface of Earth to a height h above the surface.Ignorin
Sergio [31]

Answer:

Explanation:

Potential energy on the surface of the earth

= - GMm/ R

Potential at height h

=  - GMm/ (R+h)

Potential difference

= GMm/ R -  GMm/ (R+h)

= GMm ( 1/R - 1/ R+h )

= GMmh / R (R +h)

This will be the energy needed  to launch an object from the surface of Earth to a height h above the surface.

Extra  energy is needed to get the same object into orbit at height h

= Kinetic energy of the orbiting object at height h

= 1/2 x potential energy at height h

= 1/2 x GMm / ( R + h)

8 0
3 years ago
A 1.0 kg copper rod rests on two horizontal rails 1.0 m apart and carries a current of 50 A from one rail to the other.
vagabundo [1.1K]

Answer

given,

mass of copper rod = 1 kg

horizontal rails = 1 m

Current (I) = 50 A

coefficient of static friction = 0.6

magnetic force acting on a current carrying wire is

           F = B i L

Rod is not necessarily vertical

F_x =i L B_d

F_y= i L B_w

the normal reaction N = mg-F y

static friction       f = μ_s (mg-F y )

horizontal acceleration is zero

F_x-f = 0

iLBd = \mu_s(mg-F_y )

 B_w = B sinθ

 B_d = B cosθ

iLB cosθ= μ_s (mg- iLB sinθ)

B = \dfrac{\mu_smg}{i(cos\theta +\mu_s sin\theta)}

\theta =tan{-1}{\mu_s}

\theta =tan{-1}{0.6}

\theta = 31^0

B = \dfrac{0.6\times 1 \times 9.8}{50(cos31^0 +0.6 sin31^0)}

       B = 0.1 T

4 0
3 years ago
Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?
Softa [21]

Answer:

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.

Explanation:

dehydration reaction is a conversion that involves the loss of water from the reacting molecule or ion.

Hydrolysis is defined as any chemical reaction in which a molecule of water ruptures one or more chemical bonds.

Dehydration reactions link monomers together into polymers by releasing water, and hydrolysis breaks polymers into monomers using a water molecule. Monomers are just single unit molecules and polymers are chains of monomers.

3 0
3 years ago
Consider a small car of mass 1200 kg and a large sport utility vehicle (SUV) of mass 4000 kg. The SUV is traveling at the speed
Karolina [17]

Answer:

63.9 m/s

Explanation:

Parameters given:

Mass of small car, m = 1200 kg

Mass of SUV, M = 4000 kg

Speed of SUV, V = 35 m/s

Their kinetic energy of the small car is equal to the kinetic energy of the SUV, hence:

0.5 * m * v² = 0.5 * M * V²

=> 0.5 * 1200 * v² = 0.5 * 4000 * 35²

600 * v² = 2450000

v² = 2450000/600

v² = 4083.3

=> v = 63.9 m/s

The speed of the small car is 63.9 m/s.

6 0
3 years ago
a car takes 1 hour to travel 100 km along a main road and the half hour to travel 20 km along a side road what is its average sp
kolezko [41]
80 km per hour i believe. i’ll admit i’m american so we don’t use km lol, but the math should be the same. total distance = 120km, and total time = 1.5 hours. 120/1.5 = 80.
3 0
3 years ago
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